A study links post-menopausal breast cancer to working with synthetic fibers and petroleum products when younger.

Bad news for women who’ve worked with synthetic fibers and chemicals: Canadian scientists have found that such work could increase the risk of cancer. “Occupational exposure to acrylic and nylon fibers, and to polycyclic aromatic hydrocarbons may increase the risk of developing postmenopausal breast cancer,” reports the study, published in a British medical journal called Occupational and Environmental Medicine.

The worrying study points to a long delay between exposure to these chemicals and pollutants and the actual development of cancer. For example, the study found that if a woman’s exposed to these chemicals and pollutants before her mid-30s, her risks of developing breast cancer after menopause triple. Reports Reuters:

Compared with the comparison group, the risk peaked for exposures before the age of 36, and increased with each additional decade of exposure before this age, they found.

This meant women who were exposed to acrylic fibers appeared to run a seven-fold risk of breast cancer, while those exposed to nylon fibers almost doubled their risk.

Both the scientists behind the study and those commenting on it said further studies were needed since chance or undetected bias could have played a role in the findings. In addition, Reuters reports that “the scientists said more detailed studies focusing on certain chemicals were now needed to try to establish what role chemical exposure plays in the development of breast cancer.”